Method for producing components using a flowable active medium and a forming tool.

ABSTRACT

The present invention relates to a method for producing components from a blank (P 1 -P 4 ) made of a deep-drawable material, particularly steel using a free-flowing action medium. In the course of this method, the blank (P 1 -P 4 ) is clamped in a forming device (U 1 , U 2 ) and an action medium is applied to it. The blank (P 1 -P 4 ) is then preformed by elevating the pressure (P) exercised by the action medium in a region of the blank (P 1 -P 4 ) which is restricted to a section (V 1 , V 2 ) of the blank surface and which partially covers the surface section (B 1 , B 2 ) of the blank (P 1 -P 4 ) from which the final form of the component is generated. Subsequently, the preformed blank (P 1 -P 4 ) is finish formed using a forming tool (F 1 , F 2 ). In this way, components having complex shapes may be produced with optimum exploitation of the properties of the material used.

[0001] The present invention relates to a method for producing components from a blank made of a deep-drawable material, particularly steel, using a free-flowing action medium.

[0002] For producing complex components having improved component properties while exploiting the properties of the respective blank material used, on the one hand, the forming of single blanks with the aid of fluid action media is suitable, and, on the other hand, the hydroforming of welded blanks or similar hollow bodies is suitable. For the forming of simple blanks using action media, the blanks are, as a rule, brought into their final form using a stamp or a comparable forming tool, the respective forming tool used (stamp or matrix) working against a supporting pressure applied by a fluid cushion. For hydroforming, in contrast, a cavity present between the blanks and/or in the hollow body is filled with pressure fluid and has a high pressure applied to it. Through the internal pressure generated in this way, the respective workpiece is pressed into the form predetermined by the matrix surrounding the workpiece.

[0003] For the production of deep drawn parts or hydroformed parts having complex geometries, in many cases, the production of intermediate forms is necessary, since the final contour may not be generated in one forming step. In this case, the intermediate form is, as a rule, produced in tools which operate independently from the tool used to produce the final form. This partitioning of the tools and working steps significantly elevates the necessary investment costs and, as a consequence, leads to elevation of the costs connected to the production of components of the type under discussion.

[0004] In addition to the method just described for producing intermediate forms using additional tools, these types of intermediate forms are also produced in practice through hydromechanical forming. For this method, the blanks to be formed are preformed in the actual forming tool using the action medium before the main forming. The actual finish forming, during which the final form of the workpiece is first achieved, occurs only after the preforming is finished. In order to achieve this, the preforming geometry corresponds, as a rule, at least to the outline of the forming tool element. This procedure during the preforming has been shown in many cases to be unfavorable in regard to the subsequent main forming. However, this disadvantage is countered by the advantage that greater changes in form may be achieved in the center of the component, so that targeted hardenings may be generated and the material properties may be better exploited.

[0005] The object of the present invention is to indicate a method, using which components having complex forms may be produced with optimum exploitation of the properties of the material used.

[0006] This object is achieved according to the present invention by a method of the type initially described, in which the following steps are performed:

[0007] clamping the blank in a forming device, in which the blank has the action medium applied to it on at least one side;

[0008] preforming of the blank by elevating the pressure exercised by the action medium in a region of the blank which is restricted to a section of the blank surface and partially covers the section of the blank surface from which the final form of the component is generated, and

[0009] finish forming of the preformed blank using a forming tool.

[0010] According to the present invention, partially preformed semifinished products are generated from the blank in a suitable forming device in a first working step using free-flowing action media. The final form of the component is then formed from this preformed semifinished product.

[0011] In this case, the preforming only occurs in one limited region of the blank at a time. The preforming is therefore not used, in contrast to, for example, a multistep deep drawing of components, to implement specific form elements which are shaped in a further work stroke to the final form, rather, a preform is generated which is optimally prepared, in regard to the material deformation and distribution and the exploitation of the material properties, for the required properties of the component to be finally produced. Therefore, according to the present invention, the preform is only generated in the regions in which those are necessary in consideration of the geometric properties (development) and/or component-specific properties (strength).

[0012] Depending on the requirements placed on the final product, the preforming of the blank may be performed with or without the aid of a counter mold. Preforming without a counter mold has the advantage that the material of the blank may flow unimpeded during the preforming, so that, for example, optimized strength of the preform may be achieved. However, the use of a counter mold has the advantage that the preform may also be optimally prepared in regard to its spatial arrangement for the final form to be produced. In this case, a compromise between free forming and forming entirely in a counter mold may be found in that only a part of the preformed region of the blank presses against the counter mold at the end of the preforming, while free deformation occurs in the other region.

[0013] The forming of the preformed blanks into the final form of the component is preferably performed against a supporting pressure exercised by an action medium. In this way, an exactly shaped, high-quality component may be carefully produced which, due to the careful processing, has optimized mechanical properties and a good visual appearance.

[0014] The blanks preformed according to the present invention may be connected to one another before the finish forming into the final form of the component, so that particularly large-area components or components in which the material distribution and/or the thickness of the material present in the regions of the various blanks is intentionally tailored to the loads of the component locally occurring in practical use may be manufactured. In this case, the blanks may be connected to one another using material bonding, frictional connection and/or form fit. Alternatively, blanks lying loosely on one another may also be jointly brought into the final form after the preforming.

[0015] Hollow shapes may be implemented particularly easily using the method according to the present invention if a cavity is present between the preformed blanks, which are laid on one another and possibly connected to one another. The forms formed in this way are particularly suitable for being formed into the final form of the component by hydroforming, in which the cavity has high pressure applied to it during the finish forming of the blanks into the final form.

[0016] In the following, the invention is described with reference to a drawing showing exemplary embodiments.

[0017]FIG. 1 schematically shows a blank made of thin sheet metal in a perspective view;

[0018]FIG. 2 schematically shows a component formed from the blank in a cross-section;

[0019]FIG. 3 schematically shows the blank preformed in the course of the component shown in FIG. 2 in cross-section;

[0020]FIG. 4 schematically shows another blank made of thin sheet metal in a perspective view;

[0021]FIG. 5 schematically shows a hollow shape formed by two preformed blanks of the type shown in FIG. 4 in cross-section;

[0022]FIG. 6 schematically shows another hollow shape formed by two preformed blanks of the type shown in FIG. 4 in cross-section;

[0023]FIG. 7 schematically shows a first device for preforming blanks of the type shown in FIGS. 1 or 4 in cross-section;

[0024]FIG. 8 schematically shows a second device for preforming blanks of the type shown in FIGS. 1 or 4 in cross-section;

[0025]FIG. 9 schematically shows a first device for finish forming of blanks preformed in devices of the type illustrated in FIGS. 7 or 8 in cross-section;

[0026]FIG. 10 schematically shows a second device for finish forming of blanks preformed in devices of the type illustrated in FIGS. 7 or 8 in cross-section.

[0027] In the course of the preparation of blanks P1, P2 shown in FIGS. 1 and 4, respective blanks P1, P2 are subdivided into individual regions B1, V1 and/or B2, V2. In this case, a differentiation is made between region B1 and/or B2, from each of which the finish formed component is generated, and region V1, V2, in which the preforming of respective blank P1, P2 is performed.

[0028] The position of regions V1 and/or V2 of blanks P1 and/or P2 provided for preforming is a function of the geometry of the finished component to be generated. Therefore, the development ratio over the cross-section of the finished component illustrated for exemplary purposes in FIG. 2 plays a decisive role in the layout of this region V1, V2. The geometry of partially preformed blanks P1, P2, and P3 illustrated for exemplary purposes in FIGS. 3, 5, and 6 is to be laid out in such a way that no failure occurs due to material overloading or unacceptable wrinkling during the finish forming following the preforming.

[0029] Region V1 and/or V2 provided for preforming may, if necessary, lie inside the outline of region B1 (FIG. 3), from which the component to be produced is finish formed. Its contour is indicated in FIG. 3 by dashed lines and corresponds to that shown in FIG. 2.

[0030] For another type of geometry or other requirements for the properties of the finished component, it may, however, also be necessary to perform the preforming of blank P2 in a region V2 which goes beyond of sections of respective region B2 from which the component is finished (FIG. 4). However, complete covering of region B2 by region V2, which is intended for the preforming, is also not provided in this case. Instead, the preforming only occurs in those locations where a corresponding preparation of blanks P1 and/or P2 for the following finish forming is expedient and necessary of course, the number of regions provided for preforming is not restricted to one in this case, but rather, multiple preform regions of this type may be established on one blank if necessary.

[0031] For preforming of blank P1 or a blank P4, which is subdivided corresponding to blank P2 into a region to be preformed and a region from which the final form of the component to be produced is generated, forming devices U1, U2 are used. Each of these has a container filled with a fluid action medium, for example, water. In addition, forming devices U1, U2 are each equipped with a holding device 2, which holds, on its edge regions, respective blank P1, P4 to be preformed on the edge surrounding an opening of container 1. In this way, blank P1 and/or P4 is clamped over the opening, so that its side facing the inside of the container may have the action medium applied to it. In this case, of the edge of the opening of container 1 corresponds in each case to the course of the edge of region V1 and/or V2 intended for preforming of respective processed blank P1, P4.

[0032] In contrast to forming device U1, in which, as illustrated in FIG. 7 for the example of blank P1, the preforming of blank P1 is performed without a counter mold, forming device U2 is equipped with a counter mold 3, which in this example is positioned at a distance to blank P4, clamped over the opening of container 1.

[0033] By elevating pressure P exercised by the action medium, respective blank P1 and/or P4 is arched in the region of the container opening in a movement directed outward. In this case, completely free flow of the steel material of blank P1 is permitted in forming device U1 until the end of the preforming.

[0034] In contrast, in forming device U2, preformed region V2 of blank P4 presses against counter mold 3 after a certain time of free deformation, so that a section of preformed region V2 is impressed with the shape of counter mold 3. The geometry and the dimensions of freely formed section V2 a of blank P4 are dependent in this case on the position of counter mold 3 in relation to the opening of container 1.

[0035] After the preforming in forming devices U1 or U2, blanks P1-P4 may each be individually finish formed into the respective component (FIG. 2). For this purpose, a device F1, conventionally equipped with a stamp 10 and a matrix 11, may be used, an example of which is illustrated in FIG. 9.

[0036] Alternatively, the finish forming of blanks P1-P4 may also be performed in a device F2, which has a container 20 for an action medium 21, particularly water, and a holding device 22. Preformed blank P1 is, for example, held in the opening of container 20 by holding device 22.

[0037] The finish forming of blank P1 is then performed using a stamp 23, which may be introduced into the opening of container 20 and in whose face the shape of the component to be generated is molded. During a working stroke of stamp 23, preformed blank P1 is drawn into container 20. At the same time, the action medium contained in container 20 exercises a supporting pressure S directed against the force of stamp 23, so that preformed blank P1 presses against stamp 23 as its stroke increases and thus receives the shape predetermined by stamp 23.

[0038] It is also possible to lay two blanks P2, P3, preformed in device U1, for example, on top of one another, so that they form hollow body H1 (FIG. 5) and/or H2 (FIG. 6), each of which has a preformed region V2, V3 on its top and bottom. In this case, blanks P2, P3 forming respective hollow bodies H1, H2 may be welded to one another, so that they form a unitary module. The form of the components finish formed from hollow bodies H1, H2 formed in this way is indicated in FIGS. 5 and 6 by dashed lines.

[0039] Preformed hollow bodies H1, H2 may be finish formed particularly well by having internal high pressure applied to them. For this purpose, hollow bodies H1, H2 are positioned in a matrix of a suitable device, not shown here, and filled with a free-flowing action medium, for example, water. Subsequently, the action medium has pressure applied to it, so that the sheet metal material of respective hollow body H1, H2 expands until it presses completely against the walls of the matrix. List of reference numbers  1 container,  2 holding device,  3 counter mold, 10 stamp, 11 matrix, 20 container, 21 action medium, 22 holding device, 23 stamp, F1, F2 device for finish forming, B1, B2 region from which the finish formed component is generated, H1, H2 hollow bodies, P pressure, P1, P2, P3, P4 blanks, S supporting pressure, U1, U2 forming devices, V1, V2, V3 region which the preforming of blanks P1, P2 is performed in, V2a freely deformed section of blank P4, 

1. A method for producing components from a blank (P1-P4) made of a deep-drawable material, particularly steel, using a free-flowing action medium, in which the following steps are performed: clamping the blank (P1-P4) in a forming device (U1, U2), in which the blank (P1-P4) has the action medium applied to it; preforming the blank (P1-P4) by elevating the pressure (P) exercised by the action medium in a region of the blank (P1-P4) which is restricted to a section (V1, V2) of the blank surface and which partially covers the surface section (B1, B2) of the blank (P1-P4) from which the final form of the component is generated, and finish forming of the preformed blank (P1-P4) using a forming tool (F1, F2).
 2. The method according to claim 1, characterized in that the blank (P1-P4) is preformed without a counter mold.
 3. The method according to claim 1, characterized in that the blank (P1-P4) is preformed with a counter mold (3).
 4. The method according to claim 3, characterized in that the preformed region (V1, V2) of the blank (P1-P4) partially presses against the counter mold (3) at the end of the preforming.
 5. The method according to claim 3, characterized in that the preformed region of the blank (P1-P4) presses completely against the counter mold (3) at the end of the preforming.
 6. The method according to one of the preceding claims, characterized in that the forming of the preformed blank (P1-P4) into the final form of the component is performed against a supporting pressure (S) exercised by an action medium.
 7. The method according to one of the preceding claims, characterized in that after the preforming at least two blanks (P1-P4) are connected to one another and the blanks (P1-P4) are finish formed jointly into a final form.
 8. The method according to claim 7, characterized in that the preforms are connected to one another by material bonding, friction, and/or form fit.
 9. The method according to one of claims 1 to 6, characterized in that after the preforming at least two blanks (P1-P4) are laid loosely on one another and the blanks (P1-P4) are finish formed jointly into a final form.
 10. The method according to one of claims 7 to 9, characterized in that a cavity is present between the blanks (P1-P4).
 11. The method according to claim 10, characterized in that the cavity has a high pressure applied to it during the finish forming of the blanks (P1-P4) into the final form. 